Installing a sub pannel circuit breaker box

I want to install a sub pannel in my house.
Basically i want to run a cable off of the main electricity cable coming into my home BEFORE it reaches my main fuse board. I will be needing a large amount of electricity for 1 room and it wont be safe to run this threw the wires in my House hense the extra fuse board and i dont want to run it off the main fuse board like a sub pannel because it will trip out my main curcuit breakers.

So i live in a communal zone where the electric meters are in a locked communal area so im not talking about running it before it reaches the meter.

Where the cables enter my apartment and connect to the fuse board i want to smash into the wall and run a completely seperate cable off BEFORE the main fuse board to a room and install a second fuse board with hire rated wiring and breakers

Any info on how i can do this and problems i will encounter will be great.
As to why..... My garage is a secret sun bed shop.